The present invention pertains to a method for automatically binding bundles of cables, where a continuously fed cable tie with teeth or grooves on one of its surfaces is advanced by a motor and its leading end is inserted into a lock that is provided with a locking means. The cable tie is then wound around a cable bundle and reinserted into the lock, whereafter the cable tie is tensioned by reversing the direction of feed relative to its original direction of advance and the tie is cut behind the lock. The invention also pertains to an automatically operating device for carrying out this method.
An automatic cable strap binding devise is shown in EP 0 297 337 A1. However, this device has various disadvantages. The automatic binding process is triggered with an actuating lever and is carried out by a complicated mechanism. The mechanism has numerous individual parts that are designed relative to one another for the various production steps, and thus, this device is very susceptible to malfunctions. The complicated mechanism causes the process to be carried out relatively slowly. The locks are connected to one another like a chain by means of connecting pieces. They are cyclically fed from the bottom with a mechanical drive that is connected to the actuating lever. Consequently, the locks are fed against the force of gravity. The locks are moved into a temporary position, in which they are taken hold of by a horizontally movable carriage. The carriage also contains a guide channel for supplying the continuous cable tie. The locks are ultimately positioned at the outlet opening of the device and in front of the guide channel for the cable tie. The initial positioning of an individual lock in front of the carriage against the force of gravity, is not reliable because there is no defined limit stop. Consequently, it cannot be guaranteed that the ensuing production steps are carried out error-free.
The binding device of EP 0 297 337 A1 uses a certain design of the lock for tensioning the cable tie and the cable tie design matches this lock design. One surface of the cable tie contains two teeth that are parallel but are directed opposite to one another. The locks are essentially cuboid and have through holes with matching locking tabs protruding from the opposing surfaces. These locking tabs contain matching locking teeth that each extend over half the width of the locking tabs and that are laterally offset, with the locking teeth being able to engage with the teeth of the cable tie. Once a lock is correctly positioned in the opening and aligned relative to the guide channel for the cable tie in the carriage, the cable tie is pushed forward and through the opening in the lock in a motor-driven fashion. The end of the cable tie slides along guide jaws that close around a cable bundle until the tie loops entirely around the cable bundle and is reinserted into the lock. The end of the cable tie now must be guided through the opening of the lock in the opposite direction, wherein the locking tabs should engage with opposing teeth in the cable tie. Subsequently, the cable tie is tensioned by reversing the drive until the cable bundle within the cable tie loop is pulled together tightly and the ends of the tie protruding backwards from the lock are cut off.
Malfunctions may occur, in particular when the leading end of the cable tie is reinserted into the opening of the lock after it has slid along the guide jaws. The cable tie must loop 360 degrees around the cable bundle and its end must then be returned into the opening of the lock at an acute angle. After the looping process, the leading end of the cable tie impacts the rest of the tie in front of the opening of the lock at an obtuse or right angle. In order to accomplish an insertion at an acute angle, the leading end is deflected in such a way that it is pushed into the opening. Since there is no defined limit stop for the end of the cable tie, it cannot be controlled whether the end is actually inserted into the opening and sufficiently advanced therein in order to ensure a reliable engagement of the locking tabs with the teeth of the cable tie. The end may protrude into the guide channel for the cable tie and thus cause malfunctions in the device after being cut as waste that cannot be removed.
The process of cutting the cable tie behind the lock takes place while the cable tie is still subjected to the tension required for the tensioning process. Practical experience demonstrates that the short end of the cable tie which is cut behind the lock may jump out of the lock such that the entire binding process is unsuccessful and must be repeated.
In certain instances, it is necessary to mount the bundled cables, e.g., on a carrier part or a housing wall, at certain intervals with the aid of special fastening means. The known device does not provide the option of attaching such fastening means to the cable bundles.
The present invention is based on the objective of developing a binding device that operates reliably, quickly, and without any malffunctions. After the cable tie is looped around the cable bundle and the cable tie is tightened, a reliable engagement between the locking tabs in the lock and the cable tie must be ensured, such that the engagement cannot be loosened or separated at all after the cable tie is cut behind the lock. In addition, it should be possible, if so required, to arrange a fastening means on the cable tie for anchoring the cable bundle on a carrier part simultaneously with the binding of the cable bundles.
According to the present invention, the objectives are attained due to the fact that the drive of the cable tie is stopped before the cable tie is cut such that the cable tie behind the lock is no longer subjected to tension. Therefore, the end of the cable tie will not jump out of a tooth of the locking means in the lock and will not jump completely out of the lock when the cable tie is subsequently cut.
The control of the driving motor of the cable tie and the interruption of the cable tie drive preferably take place as a function of measured values. This is achieved, in particular, by measuring the power consumption or the torque of the driving motor.
The measured value for controlling the driving motor may also be obtained in the form of a distance measurement during the advance of the cable tie. This second measured value may also serve for control purposes. Consequently, the locking means of the lock reliably engages with the grooves of the cable tie, and the cable tie cannot become loose or separate at all. In addition, the cable tie is always cut at a defined position, and the newly created end of the cable tie is reliably taken hold of in the lock during the next advance movement. The locking teeth and the grooves of the cable tie can never be positioned xe2x80x9ctooth-on-tooth.xe2x80x9d
In an automatically operating binding device, a motor-driven carriage according to the present invention can be moved back and forth in the housing. A guide channel for the cable tie ends at the upper side of the carriage, with the opening of the guide channel being covered by an insertion tab. Lateral holding jaws, between which a lock can be placed, are provided at the leading end of the carriage. The lock has a through-channel which is aligned with the insertion tab. The lock also includes an insertion channel that is open toward the bottom and offset by 90 degrees relative to the through-channel. The through-channel and the insertion channel each include locking tabs for engaging the teeth or grooves of the cable tie. At the end of the. advance movement of the carriage, the lock, which is held between the holding jaws, is placed in an outlet opening of the housing. Guide jaws include a guide groove that is aligned with the inlet end of the through-channel in the lock when the jaws are closed. The groove is aligned with the insertion channel of the lock at its outlet end. The insertion tab can be inserted into the through-channel in order to raise the locking tab such that the cable tie can be advanced in a motor-driven fashion underneath the insertion tab. The tie goes through the through-channel and along the guide groove, until it reaches the insertion channel of the lock and is able to engage the locking tab.
The housing has an outlet opening, which aligns with the guide channel when the carriage is in the advanced position.
Once the leading end of the cable tie engages in the insertion channel of the lock, the drive motor for the cable tie is switched from feeding to tensioning. The drive of the cable tie is entirely stopped once a certain tensile force is reached. Subsequently, a cutting device is actuated, wherein the knife of the cutting device moves perpendicular to the direction of advance of the cable tie behind the lock. The carriage is then returned to its starting position.
A supply tube for the locks advantageously extends into the device from the top, with the opening of the supply tube being situated directly above the space limited by the holding jaws of the carriage. Due to this measure, the locks can be reliably positioned and do not have to be transported against the force of gravity.
According to one preferred embodiment of the device according to the invention, holding devices are provided in the housing on both sides of the outlet opening. Fastening means are supplied from the top and are used for mounting the cable bundle on a carrier part. The fastening means are placed on the holding devices. A head part of these fastening means protrudes downward into the moving path of the carriage through the holding devices and contains an eyelet that is aligned with the through-channel of the lock. The fastening means are taken hold of by the carriage during its advance and moved into position in the outlet opening. Due to this measure, it is possible to bundle the cables and, if so required, attach fastening means for the cable bundle in one production step.
In order to ensure that the fastening means can be reliably driven during the carriage movement and then placed at the appropriate position, a driver is advantageously provided on the carriage. During the forward movement of the carriage, this driver engages a protruding collar of the fastening means.
A first pair of holding clamps for the lock and a second pair of holding clamps for the fastening means may be arranged in the device on both sides of the outlet opening in order to ensure the correct positioning of the lock and the fastening means in the outlet opening.
The device for supplying the fastening means, including an ejection channel for transport strips that are separated from the fastening means, is preferably arranged in an interchangeable module that can be removed from the device. If the cable bundle does not have to be anchored on a carrier part, the interchangeable module can be removed from the device and replaced with a cover.
The guide jaws surrounding the cables to be bundled are preferably closed and opened manually, with all other steps of the device being program-controlled after a trigger is actuated.
The switching of the cable tie driving motor from feeding to tensioning may also be defined by the measurable advance of the cable tie. For this purpose, a light barrier can be provided in the device within the region of the starting position or zero position of the cable tie.
A method using the device according to the invention preferably consists of the following steps:
initiating an operating cycle after the sensor has recognized a binding point for a cable bundle, with a lock being placed between the holding jaws of the carriage,
releasing or blocking the supply of fastening means after the sensor has recognized a mounting point for the cable bundle on a carrier part,
advancing the carriage to the working position of the lock and, if applicable, to that of the fastening means,
advancing the slide on the carriage and inserting the insertion tab into the through-channel of the positioned lock,
advancing the cable tie until it is inserted into the insertion channel and engaged with the locking means provided therein, during which a continuous measurement of the power consumption of the cable tie driving motor takes place,
switching the driving motor from feeding to tensioning as a function of the measured value, during which the continuous measurement of the power consumption of the driving motor continues,
returning the slide to its relative starting position on the carriage,
stopping the driving motor as a function of the measured value in order to remove tension in the cable tie behind the lock,
actuating the cutting device for cutting the cable tie behind the lock,
pulling the cable tie back to its starting position, and
returning the carriage to its starting position.